The kidneys are a pair of organs that lie in the back of the abdomen on each side of the vertebral column. The kidneys play an important regulatory role in maintaining the homeostatic balance of the body. For example, the kidneys eliminate foreign chemicals from the body, regulate inorganic substances and extracellular fluid, and function as endocrine glands, secreting hormonal substances like renin and erythropoietin.
The main functions of the kidneys are maintaining the water balance of the body and controlling metabolic homeostasis. Healthy kidneys regulate the amount of fluid in the body by making urine more or less concentrated, thus either reabsorbing or excreting more fluid, respectively. Urine production in the kidneys is regulated in part through autoregulation, which involves reflexive changes in the diameters of the arterioles supplying the nephrons, thereby altering blood flow and filtration rates. Both hormonal and neural mechanisms can supplement or adjust the local responses.
The kidneys and ureters are innervated by the renal nerves. Most of the nerve fibers involved are sympathetic postganglionic fibers from the superior mesenteric ganglion. A renal nerve enters each kidney at the hilus and follows the branches of the renal artery to reach individual nephrons. Known functions of sympathetic innervation include: (1) regulation of renal blood flow and pressure; (2) stimulation of renin release; and (3) direct stimulation of water and sodium ion resorption.
A variety of methods are currently used to treat kidney disease and conditions associated with kidney disease. For example, pharmacological compositions, such as FERRLECIT (iron gluconate) and VENOFER (iron sucrose), dialysis, and surgical intervention, such as kidney transplantation, are all used. Another method used to treat kidney disease and conditions associated with kidney disease involves electrostimulation of the renal nerves. Such electrostimulation methods, however, are often non-specific and offer only short-term symptomatic relief.